This invention relates to a method for inspecting electrical devices which have conductors covered by one or more protective layers of insulating material, to determine the quality of the protective layer or layers.
Effective inspection of electrical devices such as monolithic integrated circuit devices or other electrical or electronic devices such as hybrid integrated circuit devices, thin or thick film integrated circuit devices, and printed circuit boards, which are provided with a protective layer of insulating or passivating material over the conductors thereof, is indispensable to the production of reliable products. Careful inspection of monolithic integrated circuit devices, for example, is preferably carried out in an early stage of their production and particularly before they are diced and mounted. The early detection of unacceptable devices can result in significant savings in the cost of production. Visual inspection of integrated circuit devices is carried out at several stages in the production process, but visual inspection cannot effectively detect flaws in protective passivating material, particularly when the flaw occurs over a non-specular surface such as that of an aluminum conductor.